Beam assembly with multi-hollow formation

ABSTRACT

A beam assembly includes a first beam that has a first tubular portion and a first projecting portion that extends from the first tubular portion. A second beam has a second tubular portion and a second projecting portion that extends from the second tubular portion. The elongated interior of the first tubular portion defines a first hollow area and the elongated interior of the second tubular portion defines a second hollow area. The first beam is attached to the second beam with the first projecting portion attached to the second tubular portion and the second projecting portion attached to the first tubular portion to define a third hollow area between the first and second projecting portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-provisional applicationSer. No. 17/249,152, filed Feb. 22, 2021, which claims priority under 35U.S.0 §119(e) to U.S. Provisional Patent Application No. 62/979,457,filed Feb. 21, 2020, the disclosures of which are considered part ofthis application and are hereby incorporated by reference in theirentireties.

TECHNICAL FIELD

The present disclosure generally relates to a beam component, and morespecificity relates to a tubular beam with at least one hollow interior,such as for use as a vehicle bumper reinforcement, a structural framecomponent, a battery tray component, or the like.

BACKGROUND

Vehicle beams used for reinforcement and structural support aretypically designed for a specific vehicle application and mountinglocation on the vehicle. The cross-sectional shape of a beam used as avehicle structural component is commonly designed to have a geometricshape that corresponds with desired packaging space, bending strength,and impact energy management characteristics for the application andlocation on the vehicle architecture. Further, a roll-formed beam thatis designed for a specific component uses a customized set of rolltooling, such that alterations to a cross-sectional shape or design of aroll-formed beam often requires the costly investment in additionalcustomized roll tooling.

SUMMARY

The present disclosure provides a beam assembly that incorporatesmultiple elongated beams into a single elongated beam assembly. The beamassembly may include beam sections that are cut from a single elongatedbeam and attached together in parallel alignment with each other toprovide a more robust elongated beam structure with a desiredcross-sectional shape, such as a cross-sectional shape with multiplehollow areas and/or multiple shear walls. Thus, at least some of thebeam sections that are attached together to form the beam assembly mayindividually have the same cross-sectional shape. In doing so, desiredcross-sectional attributes of the beam assembly may be achieved withreduced tooling that may otherwise be necessary to form a singular beamwith similar cross-sectional attributes to the beam assembly.

According to one aspect of the present disclosure, a beam assemblyincludes a first beam that has a first tubular portion and a firstprojecting portion that extends from a first seam along the firsttubular portion. A second beam has a second tubular portion and a secondprojecting portion that extends from a second seam along the secondtubular portion. The elongated interior of the first tubular portiondefines a first hollow area and the elongated interior of the secondtubular portion defines a second hollow area. The first beam is attachedto the second beam with the first projecting portion attached to thesecond tubular portion and the second projecting portion attached to thefirst tubular portion to define a third hollow area between the firstand second projecting portions.

In some implementations, the first and second beams each have the samecross-sectional shape, such as a P-shaped cross-section that extendscontinuously along the length of the respective beam. Also, in someexamples with the first beam disposed vertically above the second beam,the lower wall of the first beam and the upper wall of the second beammay be substantially planar and parallel to define internal shear wallsof the beam assembly.

In further implementations, the beams may each be roll formed with ametal sheet that is made of high-strength steel, ultra-high-strengthsteel, or aluminum, among other metals. The first and second beams maybe attached together via welding, such as with continuous welding alongthe length of the first and second beams.

In other aspects, the beam assembly may include a third beam that has athird tubular portion and a third projecting portion extending from athird seam along the third tubular portion. The third beam may have thesame cross-sectional shape as the first and second beams. In someexamples, the third beam may be attached to the second beam with thethird projecting portion disposed perpendicular to the first and secondprojecting portions, such as to form a floor support for a vehiclebattery tray.

Optionally, the beam assembly may be installed as a frame component of avehicle, such as a rocker beam, a rocker insert, a floor cross member, aroof cross member, a pillar structure, or other structural vehiclecomponent. In some implementations, the beam assembly may be used as abumper reinforcement beam, a door beam, or as part of another impactenergy management structure. Further, in some examples, the beamassembly may be used as a battery tray component, such as a tray framewall or cross member.

According to another aspect of the present disclosure, a beam assemblyincludes a first beam that has a first tubular portion and a firstprojecting portion extending along the first tubular portion. The beamassembly also comprises a second beam that includes a second tubularportion and a second projecting portion extending along the secondtubular portion. The first and second beams are formed from a metalsheet, such that the first and second tubular portions each having aseam disposed along a length thereof that is defined by an edge sectionof the metal sheet attached along an intermediate section of the metalsheet. The first and second projecting portions integrally protrude atthe seam from the intermediate section of the metal sheet. The firstbeam is attached to the second beam with the first projecting portionattached to the second tubular portion and the second projecting portionattached to the first tubular portion to define a hollow area betweenthe first and second projecting portions.

These and other objects, advantages, purposes, and features of thepresent disclosure will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an upper perspective view of a vehicle schematicallyillustrating various examples of beam assemblies;

FIG. 2 is a side elevation view of the vehicle shown in FIG. 1schematically illustrating additional examples of beam assemblies;

FIG. 3 is an upper perspective view of an example beam assembly;

FIG. 3A is a cross-sectional perspective view of the beam assembly shownin FIG. 3 , taken at line A-A;

FIG. 4 is an end view of the beam assembly shown in FIG. 3 ;

FIGS. 5-7 are end views of additional examples of a beam assembly;

FIG. 8 is a side elevation view of a vehicle schematically illustratingan additional example of a beam assembly of a battery tray structure;

FIG. 9 is a cross-sectional view of a side wall portion the battery traystructure shown in FIG. 8 ; and

FIGS. 10-12 are end views of additional examples of a beam assembly.

DETAILED DESCRIPTION

Referring now to the drawings and the illustrative embodiments depictedtherein, a beam assembly is provided that may be used in various beamapplications, such as in components or structures of automotivevehicles, including electric vehicles (EVs) and internal combustionengine (ICE) vehicles, such as the vehicle 100 shown in FIGS. 1 and 2 .The beam assembly, such as those shown in FIGS. 3-7 and 9-12 ,incorporates multiple elongated beams into a single elongated beamassembly. As shown in FIGS. 3-4 , the beam assembly 10 includes a firstbeam 12 that has a tubular portion 14 with an elongated hollow interior16 and a projecting portion 18 that protrudes outward from a seam thatextends along the tubular portion 14. A second beam 22 also has atubular portion 24 with an elongated hollow interior 26 and a projectingportion 28 that protrudes outward from a seam that extends along thetubular portion 24. Thus, the first and second beams 12, 22 may eachhave the same cross-sectional shape, such as a P-shaped cross-section.With generally the same cross-sectional shape, the first and secondbeams 12, 22 may, prior to assembly, be cut from a single elongatedbeam, such as a continuous roll formed beam. The first and second beams12, 22 are attached together in parallel alignment and alongside eachother to combine in forming a desired cross-sectional shape of theoverall beam assembly 10.

To form the beam assembly 10, the first and second beams 12, 22 may bedisposed in a flipped, mirrored relationship across a longitudinal planethat extends axially between the tubular portions 14, 24 of the firstand second beams 12, 22. In other words, when starting with the firstand second beams 12, 22 in the same orientation, one of the beams isrotated axially along its longitudinal axis approximately 180 degreesrelative to the other beam prior to attaching the beams 12, 22 together.As shown for example in FIGS. 3-4 , the first beam 12 is attached to thesecond beam 22 with the projecting portion 18 of the first beam 12attached to the tubular portion 24 of the second beam 22 and theprojecting portion 28 of the second beam 22 attached to the tubularportion 14 of the first beam 12 to define at least two separateattachment points 30 or seams disposed between the beams 12, 22longitudinally along the length of the beam assembly 10. The attachmentpoints 30 may be formed with welding, such as with continuous weldedseams or intermittent spot welds, or may be formed with other types ofattachment, such as adhesive or fasteners or the like.

As shown in FIGS. 3-4 , the opposing walls 34 of the tubular portions14, 24 of the first and second beams 12, 22 that face each other may bespaced away from each other to define an elongated hollow area 32between the beams 12, 22. The hollow area 32 is also bounded between theprojecting portions 18, 28 of the beams 12, 22. With the spacing thatprovides the defined central hollow area 32 of the beam assembly 10, theopposing walls 34 of the tubular portions 14, 24 may function toreinforce the overall interior area of the beam assembly 10, such as byacting as internal shear walls of the beam assembly 10. Further, theopposing walls 34 of the beam assembly 10 divide the interior area toprovide a multi-hollow shape that is defined by the hollow interiors 16,26 of the tubular portions 14, 24 of the respective beams 12, 22 and thecentral or third hollow area 32 that is disposed between the tubularportions 14, 24. It is contemplated that additional examples of the beamassembly may have various alternative cross-sectional shapes andconfigurations, such as with additional or alternative beams, attachmentpoints or hollow areas to provide the desired cross-sectional shape ofthe beam assembly.

The perimeter cross-sectional shape of the beam assembly 10 may be arectangular shape, such as also shown in FIGS. 3-4 . In addition, thetubular portions 14, 24 may each have a generally rectangularcross-sectional shape that is defined by four orthogonally arranged wallsections. For example, as shown in FIG. 4 , the beams 12, 22 may be rollformed from a metal sheet to form the tubular portions 14, 24 with afirst wall section 34, a second wall section 36, a third wall section38, and a fourth wall section 40 that together comprise a rectangularcross-sectional shape. The tubular portions 14, 24 have three roundedcorners 42 that are defined by the bend radius of the metal sheet, whichcan be limited by the material thickness and material ductility, such asgreater than approximately four times the thickness of the metal sheet.The beams may each be roll formed with a metal sheet that is made ofhigh-strength steel, ultra-high-strength steel, or aluminum, among othermetals.

As shown in FIG. 4 , the remaining square corner 44 of the tubularportion 14, 24 is formed by an edge 46 of the first wall section 34being attached to an intermediate location on the metal sheet betweenthe fourth wall section 40 and the projecting portion 18, 28. The seamformed at the edge 46 of the metal sheet may be attached by welding theedge 46 against the metal sheet, such as with the formation of a filletweld or the like. Such welding may be done, for example, by intermittentspot welding or continuous welding along the beam. The attachmentlocation of the first wall section 34 at the sheet forms a seam andgenerally separates the fourth wall section 40 and the projectingportion 18, 28. As shown in FIG. 4 , the projecting portions 18, 28extend from the tubular portions 14, 24 in planar alignment with therespective fourth wall section 40. When the two separate beams 12, 22are attached together, the third hollow area 32 formed between the beamsis surrounded by the projecting portions 18, 28 and the fourth wallsections 40 of the tubular portions 14, 24.

With further reference to FIGS. 3-4 , the tubular portions 14, 24 mayeach include a recessed area 48 to receive the edge of the projectingportion 18, 28 of the other beam. The recessed area 48, shown in FIG. 4, is disposed at the second wall section 36 and has a depth protrudinginward into the respective hollow interior area 16, 26 a distancegenerally equal to the thickness of the engaged edge of the projectingportion 18, 28. The approximate depth of each recessed area 48 shown inFIG. 4 is measured between the planar outer surface of the second wallsection 36 and the planar outer surface at the recessed area 48, whichis generally equal to the thickness of the metal sheet of the otherbeam. The recessed area 48 generally aligns the planar outer surface ofthe second wall section 36 with the outer surface of the attachedprojecting portion 18, 28, which may also be aligned with the outersurface of the fourth wall section 40 from which the respectiveprojecting portion 18, 28 extends. The aligned projecting portions 18,28, second wall sections 36, and fourth walls sections 40 together formparallel and opposing outer walls of the overall beam assembly 10.

Referring now to FIGS. 5-10 , additional examples of a beam assembly 110(FIG. 5 ), 210 (FIG. 6 ), 310 (FIG. 7 ), 410 (FIG. 8 ), 510 (FIG. 9 ),610 (FIG. 10 ) are shown that illustrate alternative cross-sectionalshapes from that illustrated in FIGS. 3-4 . For example, in theorientation shown in FIG. 5 , the beam assembly 110 has a reducedhorizontal width from the beam assembly 10 shown in FIG. 4 . The reducedwidth of the beam assembly 110 is provided by the tubular portions 114,124 of each beam 112, 122 having a reduced width, and more specifically,the first and third wall sections 134, 138 having a shorter length. Thebeam assembly 110 shown in FIGS. 5 may be formed with generally the samelength of the second and fourth wall sections 136, 140, same length ofthe projecting portion 118, 128, and same number of bends as the beamassembly 10 shown in FIG. 4 . However, the radius of curvature at thecorner bends 142 is larger in FIG. 5 than the corner bends 42 in FIG. 4and the overall width of the metal sheet used to form each beam 112, 122the beam assembly 110 in FIG. 5 is less than the width of the metalsheet used to form the beams 12, 22 in FIG. 4 .

Moreover, as shown in the orientation in FIG. 6 , the beam assembly 210has the same rectangular perimeter cross-sectional shape as the beamassembly 10 shown in FIG. 4 , but has internal sheer walls locatedcloser together. The closer shear walls are provided by the tubularportions 214, 224 of each beam 212, 222 having an increased height, andmore specifically, the second and fourth wall sections 236, 240 having alonger length. To maintain the same overall height of the beamassemblies 10, 210 in FIGS. 4 and 6 , the projecting portions 218, 228of the beam assembly 210 in FIG. 6 are reduced in length by the samegeneral length that the tubular sections are increased in height. Thus,the dimensional alterations shown in FIGS. 6 may be formed with the samemetal sheet, bend configurations, and roll tooling, but altering thepositions of the roll tooling on the roll forming line. Thus, the beamassembly in different examples may include various dimensionalvariations.

The beam assembly may also include one or more channel ribs to stiffen aportion of the beam assembly. As shown for example in FIG. 7 , theprojecting portions 318, 328 of the beam assembly 310 each include achannel rib 320 at a central section thereof and extending along alength of the respective beam 312 322. By locating the channel ribs 320on the projecting portions 318, 328, the channel ribs 320 are disposedat a central vertical location of the beam assembly 310 and protrudeinto opposing sides of the central or third hollow area 332. The beamassembly 310 shown in FIG. 7 is otherwise similar to the beam assembly10 shown in FIG. 4 , such that the channel rib alterations may be madeby increasing the width of the metal sheet and adding roll tooling thatforms a channel rib 320 in the projecting portion. In further examples,it is contemplated that additional channel ribs may be provided on otherportions of a beam assembly, such as at wall sections of the tubularportions.

As further shown in FIG. 8 , the beam assembly 410 has the same generalcross-sectional shape as the beam assembly 10 shown in FIG. 4 , exceptfor the attachment of the edge portion 446 of the first wall section 434to the metal sheet. As shown in FIG. 8 , the seam formed at the edgeportion 446 of the metal sheet may include a corner bend 442, so thatthe a planar side surface of the metal sheet at the edge portion 446attaches to the planar side surface of the metal sheet between thefourth wall section 440 and the projecting portion 418, 420. This flatsurface attachment may be provided by welding, for example, byintermittent spot welding or continuous welding along the beam. Forinstance, a laser weld may be formed by orienting the laser headgenerally perpendicular to the exterior surface of the metal sheet, suchthat the laser weld may be formed perpendicularly through the portion ofthe metal sheet that overlaps the edge portion 446. As shown in FIG. 8 ,the edge portions 446 are bent to extend into the hollow interior areas416, 426 of the respective beams 412, 422. As shown in FIG. 8 , theprojecting portions 418, 428 extend from the tubular portions 414, 424in planar alignment with the edge portions 446 and the respective fourthwall section 440.

Similarly, as shown in FIG. 10 , the beam assembly 610 has the samegeneral cross-sectional shape and edge portion attachment as the beamassembly 410 shown in FIG. 8 , except for the attachment of theprojecting portions 618, 628 to the tubular portions 614, 624 of theother respective beam. As shown in FIG. 10 , the edges of the projectingportions 618, 628 may also include a corner bend 642, so that the aplanar side surface of the metal sheet at the projecting portion 618,628 attaches to the planar side surface of the first wall section 634.This flat surface attachment may be provided by welding, for example, byintermittent spot welding or continuous welding along the beam. Forinstance, a laser weld may be formed along the crevice seam by orientingthe laser head generally perpendicular to the exterior surface of thesecond wall section 636 and the projecting portions 618, 628. Also, asshown in FIG. 10 , the edges of the projecting portions 618, 628 arebent to extend into the central interior areas 632. In doing so, therecessed area may be omitted from the second wall section.

Furthermore, as shown in FIG. 9 , the projecting portions 518, 528attach at the tubular portions 514, 524 and extend beyond the tubularportion to provide a flange 550, 552 for attaching to an adjacentvehicle component. For example, the flanges 550, 552 may be used toattach the beam assembly 510 between inner and outer rocker sills or maybe used in place of either or both rocker sill components. The flangesmay be alternatively shaped or located in different examples to providea design that accommodates the corresponding vehicle design. As shown inFIG. 9 , the projecting portions 518, 528 are disposed over the oversecond wall sections 536 and each have a bend that corresponds with thecorner bend 542 between the second wall section 536 and the third wallsection 538, such that the projecting portions 518, 528 follow along andover the third wall sections 538. As further shown in FIG. 9 , theprojecting portions have an outward directing bend that directs theflanges 550, 552 orthogonally outward from the third wall section 538.

Referring now to FIGS. 11 and 12 , the beam assembly 710 includes athird beam 752 that has a tubular portion 754 with an elongated hollowinterior 756 and a projecting portion 758 that extends from the tubularportion 754. As shown in FIG. 12 , the third beam 752 has the samecross-sectional shape as the first and second beams 712, 722, shown as aP-shaped cross-section. As such, the three beams 712, 722, 752 may becut from a single elongated beam, such as a continuous roll formed beam.The beams 712, 722, 752 are attached together in parallel alignment andalongside each other to combine in forming a desired cross-sectionalshape of the beam assembly 710, which has four hollow interior areas.

As further shown in FIGS. 11 and 12 , the third beam 752 is attached tothe second beam 722 with the projecting portion 758 of the third beam752 arranged perpendicular to the other projecting portions 718, 728 andis attached to a lower wall section 738 of the lower tubular portion.The first wall section 734 of the tubular portion 754 of the third beam752 is also attached to the lower tubular portion at the second wallsection 736. With such a cross-sectional shape, the beam assembly 710shown in FIG. 12 can be used as a side wall 760 of a battery tray 762,such as shown in FIG. 11 . The tubular portion 754 of the third beam 752may be arranged on an outboard side of the side wall 760 to aid withside impact energy absorption. Also, the projecting portion 758 of thethird beam 752 may be arranged on an inboard side of the side wall 760to form a floor support for a floor 764 of the battery tray 762, as wellas any additional interior component of the battery tray 762.

With respect to the various vehicle applications, the beam assembly maybe used, for example, as a vehicle bumper reinforcement, a structuralframe component, a battery tray component. As shown for example in FIGS.1 and 2 , these include, for example, roof bows 102, headers 103,pillars 104, rockers 105, floor cross members 106, bumper beams 107,door beams 108, frame rail tips 109, and the like. As shown in FIGS. 1and 2 , the beam assembly may be designed to undergo various impactforces, such as for vehicle bumper reinforcement beams 107 and doorbeams 108 and the like. As further provided in the exemplary vehicle 100shown FIGS. 1 and 2 , a body structure or frame 101 of the vehicle 100has multiple structural beam components, one or all of which may beprovided as a beam assembly as described herein. For example, the beamassembly may be designed to support and sustain different loadingconditions, such as for supporting horizontal spans, like a roof bow 102and a rocker rail 105 or insert thereof, or for supporting axial loads,like the pillars 104 of the vehicle frame. Furthermore, as shown on thevehicle 700 in FIG. 11 , the beam assembly may be used as a structuralcomponent of a battery tray 762, such as a perimeter side wall 760 orcross-member beam that spans between opposing side walls of the batterytray.

The cross-sectional shape of the beam assembly may include variousshapes and thicknesses for the desired application of the beam assembly,such as an open profile or a closed profile, which may include amulti-tubular profile that has two or more hollow interior areas thatextend longitudinally within the pultruded profile.

For purposes of this disclosure, the terms “upper,” “lower,” “right,”“left,” “rear,” “front,” “vertical,” “horizontal,” and derivativesthereof shall relate to the appliance as oriented in FIG. 1 . However,it is to be understood that the appliance may assume various alternativeorientations, except where expressly specified to the contrary. It isalso to be understood that the specific devices and processesillustrated in the attached drawings and described in this specificationare simply exemplary embodiments or implementations. Accordingly, theterminology that has been used is intended to be in the nature of wordsof description rather than of limitation. Hence, specific dimensions andother physical characteristics relating to the embodiments orimplementations disclosed herein are not to be considered as limiting,unless the claims expressly state otherwise. Many modifications andvariations of the embodiments and implementations are possible in lightof the above teachings.

What is claimed is:
 1. A beam assembly comprising: a first beamcomprising a first metal sheet, the first metal sheeting forming anenclosed portion and a remaining portion of the first metal sheetextending along the enclosed portion of the first beam; and a secondbeam having a second metal sheet, the second metal sheet forming anenclosed portion, wherein the first beam is attached to the second beamwith the remaining portion of the first metal sheet attached to theenclosed portion of the second beam to define a hollow area between thefirst and second beams.
 2. The beam assembly of claim 1, wherein thesecond beam comprises a projecting portion extending along the enclosedportion.
 3. The beam assembly of claim 2, wherein the projecting portionof the second beam is attached to the enclosed portion of the firstbeam.
 4. The beam assembly of claim 2, wherein a wall of the enclosedportion of the first beam comprises a planar section and a recessedsection, and wherein the projecting portion of the second beam isattached in the recessed section of the first beam.
 5. The beam assemblyof claim 1, wherein the first beam and the second beam each comprise asame cross-sectional shape.
 6. The beam assembly of claim 1, wherein thefirst beam comprises a P-shaped transverse cross section.
 7. The beamassembly of claim 6, wherein the P-shaped transverse cross sectionextends continuously along a length of the first beam.
 8. The beamassembly of claim 1, wherein the first and second beams are attachedtogether via welding.
 9. The beam assembly of claim 1, wherein theenclosed portion of the first beam comprises at least threesubstantially planar wall sections, and wherein the remaining portion ofthe first metal sheet extends from the enclosed portion in planaralignment with one of the wall sections.
 10. The beam assembly of claim1, wherein the enclosed portion of the first beam has a seam disposedalong its length, the seam defined by an edge section of the first metalsheet attached along an intermediate section of the first metal sheet,and wherein the remaining portion of the first metal sheet protrudes atthe seam from the intermediate section of the first metal sheet.
 11. Abeam assembly comprising: a first beam comprising a first metal sheetthat forms a first enclosed portion and a first projecting portionextending along the first enclosed portion; and a second beam comprisinga second metal sheet that forms a second enclosed portion and a secondprojecting portion extending along the second tubular portion, whereinthe first beam is attached to the second beam with the first projectingportion attached to the second enclosed portion and the secondprojecting portion attached to the first enclosed portion to define ahollow area surrounded by the first and second enclosed portions and thefirst and second projecting portions.
 12. The beam assembly of claim 11,wherein a cross-sectional shape of the first beam and the second beamtaken transverse to their lengths each comprise a P-shape.
 13. The beamassembly of claim 11, wherein a cross-sectional shape of the first beamand the second beam taken transverse to their lengths extendcontinuously along their respective lengths.
 14. The beam assembly ofclaim 11, wherein the first and second beams are attached together viawelding.
 15. The beam assembly of claim 11, wherein a wall of theenclosed portion of the first beam comprises a planar section and arecessed section, and wherein the projecting portion of the second beamis attached in the recessed section of the first beam.
 16. The beamassembly of claim 11, wherein the first enclosed portion comprises atleast three substantially planar wall sections, and wherein the firstprojecting portion of the first metal sheet extends from the firstenclosed portion in planar alignment with one of the wall sections. 17.The beam assembly of claim 16, wherein the first and second beams eachinclude a channel rib disposed along their respective length.
 18. Thebeam assembly of claim 11, wherein the first enclosed portion has a seamdisposed along its length, the seam defined by an edge section of thefirst metal sheet attached along an intermediate section of the firstmetal sheet, and wherein the first projecting portion of the first metalsheet protrudes at the seam from the intermediate section of the firstmetal sheet.
 19. A beam assembly comprising: a first beam comprising afirst metal sheet, the first metal sheeting forming a first enclosedportion and a first projecting portion extending along the firstenclosed portion; and a second beam having a second metal sheet, thesecond metal sheet forming a second enclosed portion and a secondprojecting portion extending along the second enclosed portion, whereinthe first beam is attached to the second beam with the first projectingportion of the first beam attached to the second enclosed portion of thesecond beam and the second projecting portion of the second beamattached to the first enclosed portion of the first beam to define ahollow area between the first and second beams.
 20. The beam assembly ofclaim 19, wherein the first enclosed portion has a first seam disposedalong its length, the first seam defined by an edge section of the firstmetal sheet attached along an intermediate section of the first metalsheet, and wherein the second enclosed portion has a second seamdisposed along its length, the second seam defined by an edge section ofthe second metal sheet attached along an intermediate section of thesecond metal sheet.